Nonnegative integers repeated 4 times.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =1a(6) =1a(7) =1a(8) =2a(9) =2a(10) =2a(11) =2a(12) =3a(13) =3a(14) =3a(15) =3a(16) =4a(17) =4a(18) =4a(19) =4a(20) =5a(21) =5a(22) =5a(23) =5a(24) =6a(25) =6a(26) =6a(27) =6a(28) =7a(29) =7